Methods and systems for real-time assessment of cells in encapsulation devices pre-and post-transplantation

ABSTRACT

Methods and systems for measuring viability and function of islet cells or stem cell-derived beta cells in an implantable device featuring setting the temperature of the cells in the implantable device to a low temperature to reduce metabolic levels of the cells and reduce oxygen requirements of the cells, and measuring oxygen consumption rates. An oxygen sensor at the inlet of the implantable device and an oxygen sensor at the outlet of the implantable device are used to calculate oxygen consumption rates of the cells, which in turn are indicative of viability. The reduction in temperature can also be used for loading cells into the implantable devices to help reduce ischemic and/or physical injury. The present invention may be used with other cell types, e.g. hepatocytes, heart cells, muscle cells, etc.

CROSS REFERENCE

This application claims priority to U.S. Patent Application No. 62/417,039, filed Nov. 3, 2016, the specification(s) of which is/are incorporated herein in their entirety by reference.

FIELD OF THE INVENTION

The present invention relates to methods and systems for assessing in real-time various parameters of cells housed in encapsulation devices. Parameters may include insulin secretion levels and oxygen consumption rates or any other appropriate parameter.

BACKGROUND OF THE INVENTION

It can be important to know whether or not cells in an encapsulation device are healthy and viable and functional both before the cells are transplanted and after the cells are transplanted. The present invention features methods and systems for monitoring cells (e.g., cell viability, function, etc., e.g., via measuring oxygen consumption rates, insulin secretion levels, etc.) in an encapsulation device in real-time before and after transplantation. The present invention also features methods of helping to reduce cell damage (e.g., ischemic damage, physical damage, etc.) during the loading process of an encapsulation device, e.g., before implantation, before and during storage, etc.

The present invention may be usable for other cell types (not just for diabetes treatment). For example, cells may include hepatocyte for bio artificial liver, heart cells, muscle cells, etc.

The disclosures of the following U.S. patents are incorporated in their entirety by reference herein: U.S. Pat. No. 5,713,888; U.S. Pat. App. No. 2003/0087427.

SUMMARY OF THE INVENTION

The present invention features systems, e.g., systems for measuring oxygen consumption rate (OCR) of cells, or measuring other features such as insulin secretion, pH, lactate, CO2 levels, etc. In some embodiments, the system comprises a bioreactor with an inlet and an outlet, wherein a first oxygen sensor is disposed at the inlet and a second oxygen sensor is disposed at the outlet; an encapsulation device comprising a lumen with the cells, and a vascularizing membrane, the encapsulation device is housed in the bioreactor; a combined heat and gas exchanger for heating liquid media to at least one temperature from 7° C. to 27° C. (or from 7° C. to 37° C.) and for allows oxygen to be controlled from 0 to 100%; and a pump for pumping liquid media from the heat exchanger to the bioreactor via the inlet and out the outlet. Oxygen sensors detect oxygen levels of the media for determining oxygen consumption rate of the cells.

In some embodiments, the bioreactor is encased in an incubator that can adjust and control temperature and oxygen, e.g. a temperature from 4-40 C, oxygen level from 0 to 100%.

In some embodiments, the system comprises a sample removal outlet for obtaining a media sample after the outlet of the bioreactor. The media sample may be for measuring insulin secretion. In some embodiments, the gas exchanger or combined heat and gas exchanger provides oxygen to the media. In some embodiments, oxygen production in the media can be shut off.

In some embodiments, the media sample is for measuring insulin, glucagon, pancreatic polypeptide, c-peptide, a hormone, or a combination thereof. In some embodiments, the media sample is for measuring chemical release (secretion) as affected by a variety of secretagogues and chemical agents that can be introduced in the system (such as glucose, arginine, KCl, GLP-1).

In some embodiments, the cells are islet cells or stem cell-derived beta cells. In some embodiments, the system comprises a glucose sensor, a lactate sensor, a pH sensor, a CO₂ sensor, or a combination thereof. In some embodiments, the oxygen sensors are operatively connected to a system for regulating an amount of oxygen delivered to the cells. In some embodiments, the system for regulating an amount of oxygen delivered to the cells can adjust a level of oxygen supplied to the cells based on a command received based on an oxygen level determined by the oxygen sensors.

The present invention also features methods for measuring oxygen consumption rate (OCR) of cells or other features (e.g., insulin secretion, etc., as described herein). The method may comprise pumping media at a temperature from 7° C. to 27° C. through a system comprising: a bioreactor with an inlet and an outlet, wherein a first oxygen sensor is disposed at the inlet and a second oxygen sensor is disposed at the outlet; and an encapsulation device comprising a lumen with the cells, and a vascularizing membrane, the encapsulation device is housed in the bioreactor; wherein the oxygen sensors detect oxygen levels of the media for determining oxygen consumption rate of the cells.

In some embodiments, the heat exchanger is separate from the gas exchanger. In some embodiments, the heat exchanger is combined with the gas exchanger.

The present invention also features methods for measuring oxygen consumption rate (OCR) of cells or other features (e.g., insulin secretion, etc., as described herein). The method may comprise pumping media at a temperature from 7° C. to 27° C. through a system according to the present invention; wherein the oxygen sensors detect oxygen levels of the media for determining oxygen consumption rate of the cells.

The present invention also features methods of measuring viability of cells. In some embodiments, the method comprises (in system with an encapsulation device with cells receiving exogenous oxygen, said cells comprising islet cells or stem cell-derived beta cells), discontinuing delivery of exogenous oxygen to the cells; setting the temperature of the cells in the encapsulation device to a temperature from 7° C. to 27° C.; and measuring oxygen consumption rate (OCR), wherein a certain OCR level is indicative of the presence of viable cells.

The present invention also features methods of measuring viability of cells. In some embodiments, the method comprises (in system with an encapsulation device with cells receiving exogenous oxygen, said cells comprising islet cells or stem cell-derived beta cells), discontinuing delivery of exogenous oxygen to the cells; setting the temperature of the cells in the encapsulation device to a temperature from 7° C. to 27° C.; and measuring oxygen consumption rate (OCR), wherein an certain OCR level is indicative of the presence of enough viable cells for implantation of the encapsulation device.

In some embodiments, the aforementioned methods comprise raising the temperature to 37° C., and measuring glucose-stimulated insulin secretion (GSIS) of the cells. In some embodiments, the aforementioned methods comprise raising the temperature to 37° C., and measuring glucose-stimulated insulin secretion (GSIS) of the cells, wherein an insulin secretion level within a threshold level or above a threshold level are indicative of the presence of enough viable and functional cells for implantation of the encapsulation device.

Other parameters include the release (secretion by the cells) of other chemical, hormone/polypeptide release (such as glucagon, c-peptide, pancreatic polypeptide) which can be induced or inhibited by secretagogues or other chemical agents (such as glucose, arginine, KCl, GLP-1).

In some embodiments, an oxygen sensor is disposed at both an inlet and an outlet of a bioreactor holding an encapsulation device with the cells. In some embodiments, the system further comprises a glucose sensor, a lactate sensor, a pH sensor, a CO₂ sensor, or a combination thereof.

The present invention also features a method of loading cells into an encapsulation device receiving exogenous oxygen (the cells comprising islet cells or stem cell-derived beta cells). In some embodiments, the method comprises lowering the temperature of the encapsulation device to a particular low temperature (e.g., 4 to 8 C, 7 to 15 C, etc.); and loading cells into the encapsulation device via a cell loading port, wherein the low temperature helps minimize ischemic or physical damage to the cells.

In some embodiments herein, exogenous oxygen is delivered to the device at a level of about 40% oxygen.

In some embodiments, the encapsulation device is held in a reservoir, said reservoir adapted to hold the encapsulation device in media. In some embodiments, the encapsulation device comprises tubing for providing cooling medium or oxygen to one or more layers of cells. In some embodiments, the oxygen sensors are operatively connected to a system for regulating exogenous delivery of oxygen to the cells.

Any feature or combination of features described herein are included within the scope of the present invention provided that the features included in any such combination are not mutually inconsistent as will be apparent from the context, this specification, and the knowledge of one of ordinary skill in the art. Additional advantages and aspects of the present invention are apparent in the following detailed description and claims.

BRIEF DESCRIPTION OF THE DRAWINGS

The features and advantages of the present invention will become apparent from a consideration of the following detailed description presented in connection with the accompanying drawings in which:

FIG. 1A shows an example of a single-chamber encapsulation device for holding cells or tissues. The device comprises a port to access the lumen for loading the cells or tissue.

FIG. 1B shows a cross-sectional view of the device of FIG. 1A. The cells are encapsulated in a two-layer membrane envelope formed using a mesh insert. The device comprises a vascularization membrane and an immunoisolation membrane. The present invention is not limited to devices that utilize an immunoisolation membrane: in some embodiments, the device only comprises the vascularization membrane.

FIG. 2A shows a detailed view of an encapsulation device with an immunoisolation membrane. The device features two chambers or lumens separated by a gas channel.

FIG. 2B shows a detailed view of an encapsulation device without the immunoisolation membrane. The device features two chambers or lumens separated by a gas channel.

FIG. 3A shows a schematic view of a system comprising a bioreactor and encapsulation device with cells disposed therein. Liquid media flows in via an inlet (which may comprise a flow cell with an oxygen sensor) and flows out of an outlet (which may comprise a flow cell with an oxygen sensor). In some embodiments, the encapsulation device is a single chamber device. In some embodiments, the encapsulation device is a dual chamber device with a gas channel (e.g., oxygen channel) disposed between the chambers (e.g., to allow for higher density). In some embodiments, the sensors on the inlet and outlet are for oxygen consumption rate measurements (which may be used as a means of evaluating viability of the device with cells).

FIG. 3B shows a schematic view of a dual chamber device that may be present in a system of FIG. 3A. The gas channel may be sealed or gas may be vented through the tubing of the gas channel.

FIG. 4 is a schematic view of a system of the present invention.

DETAILED DESCRIPTION OF THE INVENTION Encapsulation Devices

Encapsulation devices are devices for holding cells or tissues. The encapsulation device (110) shown in FIG. 1A is a single-chamber encapsulation device. The device (110) comprises an inner lumen for holding the cells (102) or tissue and at least one membrane, e.g., a vascularization membrane (120), which is impermeable to cells. In some embodiments, the device (100) further comprises an immunoisolation membrane (130). Non-cell factors or molecules (150) can escape the cell impermeable membrane. The device (110) also comprises a port (180) to access the lumen for loading the cells or tissue. FIG. 1B shows a cross-sectional view of an encapsulation device. The cells are encapsulated in a lumen (114) by a two-layer membrane envelope, a vascularization membrane (120) and an immunoisolation membrane (130). The device (110) also has structural support, e.g., mesh, seals, etc. Vasculature may grow around the device (110)

In some embodiments, the encapsulation devices (110) comprise a vascularization membrane (120) and immunoisolation membrane (130). In some embodiments, the encapsulation devices (110) comprise just the vascularization membrane (120). This allows blood vessels to grow within the transplanted tissue.

In the examples shown in FIG. 1A and FIG. 1B, the cells therein are about 5-15 μm in diameter. The outer membrane, the vascularization membrane (120), has a pore size from 5-10 μm. The vascularization membrane (120) is about 15 μm thick. The immunoisolation membrane (130) has a pore size of about 0.4 μm. The immunoisolation membrane (130) is about 30 μm thick. In some embodiments, the membranes (120, 130) are constructed from materials such as polytetraflouroethylene (PTFE) or other similar material. The present invention is not limited to the aforementioned pore sizes and thicknesses of the membranes used therein. The present invention is not limited to the aforementioned materials.

The encapsulation devices (110) may be constructed in various shapes and sizes and with various lumen volumes. For example, in some embodiments, the lumen has a volume of about 4.5 μl. In some embodiments, the lumen has a volume of 20 μl. In some embodiments, the lumen has a volume of 40 μl. In some embodiments, the device (110) is from 4 to 5 cm in length. In some embodiments, the device (110) is from 2 to 5 cm in length, e.g., 3 cm. In some embodiments, the device (110) is from 5 to 10 cm in length. The present invention is not limited to the aforementioned dimensions and lumen volumes. For example, in some embodiments, the lumen has a volume of about 100 μl. In some embodiments, the lumen has a volume of about 200 μl. In some embodiments, the lumen has a volume from 2 to 50 μl. In some embodiments, the lumen has a volume from 10 to 100 μl. In some embodiments, the lumen has a volume from 40 to 200 μl. In some embodiments, the lumen has a volume from 100 to 300 μl. In some embodiments, the lumen has a volume from 200 to 500 μl.

In some embodiments, within the encapsulation devices (110), there may be layers of cells or tissue, e.g., multiple lumens within the device (110). For example, an encapsulation device (110) may comprise two chambers or lumens. In some embodiments, the device comprises more than two chambers or lumens, e.g., 3 chambers or lumens, 4 chambers or lumens, 5 chambers or lumens, etc. FIG. 2A and FIG. 2B show examples of an encapsulation with two lumens (two chambers) that are separated by a gas channel (160). FIG. 2A and FIG. 2B also show vascularizing membrane and microvasculature. The blood vessels embed into the vascularizing membrane.

In some embodiments, the chamber or lumen comprises a single layer of cells. In some embodiments, the chamber or lumen comprises two layers of cells. In some embodiments, the chamber comprises three or more layers of cells. In some embodiments, islet spheroids (about 150 um in size) are used (shown in FIG. 2A, FIG. 2B). In some embodiments, a dual layer of the islet spheroids is used (lumen thickness would be about 300 um in the chamber or in each chamber). In some embodiments, a third layer is supported depending on the metabolic activity and other characteristics of the spheroids/cells used. Note spheroids may not be touching each other in some configurations and the space between them may be 1 or 2 spheroids apart (e.g., 150 um, 300 um), or more or less.

Methods and Systems for Monitoring Cells

FIG. 3A shows a schematic view of a system (100) comprising a bioreactor and encapsulation device with cells disposed therein. Liquid surrounds the encapsulation device (110). In some embodiments, the encapsulation device is a single chamber device. In some embodiments, the encapsulation device is a dual chamber device with a gas channel (e.g., oxygen channel) disposed between the chambers (e.g., to allow for higher density). Liquid media flows in via an inlet (106) (which may comprise a flow cell (412) with an oxygen sensor (410)) and flows out of an outlet (107) (which may comprise a flow cell (412) with an oxygen sensor (410)). In some embodiments, the sensors on the inlet and outlet are for oxygen consumption rate measurements (which may be used as a means of evaluating viability and health of the cells).

FIG. 3B shows a schematic view of a system that comprises a dual chamber device (e.g., used in a system shown in FIG. 3A) having a first chamber (113 a) and a second chamber (113 b) separated by a gas channel (160). Gas (e.g., air, oxygen) is delivered through the middle of the chambers via the gas channel to support viability and function of the cells. The gas channel does not leak into the media of the bioreactor, and does not cause leakage of the media in the bioreactor (it is separate from the media and inlet/outlet of the bioreactor).

Insulin secretion requires physiological temperature, so the evaluation of cells in the device for insulin secretion needs to be done at 37° C. (assessments at lower temperatures are not accurate).

Oxygen consumption rate (OCR) cannot be accurately evaluated with gas flowing through the gas channel. For OCR, gas flow needs to stop, but the temperature is reduced so that there is sufficient oxygen to the cells in the center of the device and the OCR is not oxygen limited.

OCR measurements may be performed at temperatures at temperature below 37° C. (e.g., 7° C. to 27° C., e.g., 7° C., 8° C., 9° C., 10° C., 11° C., 12° C., 13° C., 14° C., 15° C., 16° C., 17° C., 18° C., 19° C., 20° C., 21° C., 22° C., 23° C., 24° C., 25° C., 26° C., 27° C., etc.). Temperature may be adjusted to lower values as a function of metabolic activity and cell density within the devices. OCR is predictably dependent on temperature so that the health of the cells can still be estimated by appropriate temperature correction (Arrhenius type relationship). For example, OCR declines predictably with decreasing temperature in the range of 7° C. to 37° C.

FIG. 4 is a schematic view of a system of the present invention. A bioreactor (105) houses an encapsulation device (110), e.g., a single chamber, a dual chamber, etc., with cells. Media may be pumped via a pump through a heat or gas exchanger (or combined heat and gas exchanger), which may bring the media to a particular temperature and to a particular oxygen level. Media then flows through the inlet (106) and through an oxygen sensor (410), through the bioreactor (105) and out the outlet (107) and through the other oxygen sensor (410). Samples (for insulin secretion evaluation) may be obtained from a point outside of the outlet. The media may, for example, be recycled and flow though a water bath or incubator. Or, the media may be discarded.

In some embodiments, the combined heat and gas exchanger (or the separate heat exchanger) heats the media to a temperature between 7° C. to 37° C. (Evaluation of insulin secretion may be performed at 37° C., and then the temperature may be lowered for OCR measurements.) In some embodiments, the gas exchanger oxygenates the media to a percentage from 0-100% (e.g., 40%). Oxygen levels may be selected depending on the amount of exposure time.

For insulin secretion function measurements, high oxygen (e.g., 40% oxygen) may be present in the middle of the dual cell chamber device (along with a temperature of 37° C.).

For oxygen consumption rate (OCR) measurements, no gas is provided to the middle of the dual cell chamber. Temperature is reduced (e.g., to a temperature between 7° C. and 17° C.).

The present invention features methods and systems for monitoring cells (e.g., cell viability, oxygen consumption rates, insulin secretion levels, etc.) in an encapsulation device in real-time before transplantation (e.g., during storage) and/or after transplantation. FIG. 3 and FIG. 4 show examples of systems and devices for storing cells in encapsulation devices. These devices may be equipped with sensors (410) and readers and other features to help with real-time measurements of parameters of the cells to determine cell viability.

In some embodiments, the media is at a temperature from 4 to 8° C., e.g., 4° C., 5° C., 6° C., 7° C., 8° C. In some embodiments, the media is at a temperature from 2 to 8° C. In some embodiments, the media is at a temperature from 4 to 10° C. In some embodiments, the media is at a temperature from 2 to 15° C. In some embodiments, the media is at a temperature from 10 to 20° C. In some embodiments, the media is at a temperature from 20 to 30° C. In some embodiments, the media is at a temperature from 30 to 38° C. In some embodiments, the oxygen levels are around 40%. In some embodiments, the oxygen levels are less than 40% or more than 40%. In some embodiments, the oxygen level is from 0-5%. In some embodiments, the oxygen level is from 5-15%. In some embodiments, the oxygen level is from 15-25%. In some embodiments, the oxygen level is from 25-35%. In some embodiments, the oxygen level is from 35-40%. In some embodiments, the oxygen level is from 40-50%. In some embodiments, air is used (e.g., oxygen level is about 21%). The present invention is not limited to these temperatures or oxygen levels. Oxygen levels may vary as well. In some embodiments, a particular oxygen level is used initially and then the oxygen level is increased or decreased at a later time. In some embodiments, oxygen is turned on and then off. In some embodiments, oxygen is turned off and then on. In some embodiments, oxygen is turned on and off in a cycle for a period of time or indefinitely.

One or more sensors (e.g., two sensors, three sensors, four sensors, etc.) are integrated into the system, e.g., operatively connected to the encapsulation device or positioned appropriately in proximity to the encapsulation device. The sensors can help measure oxygen consumption rates, insulin secretion level, glucose levels, lactate levels, pH levels, carbon dioxide levels, or a combination thereof.

For example, in some embodiments, a first oxygen sensor is disposed at an inlet of the encapsulation device and a second oxygen sensor is disposed at an outlet of the encapsulation device, wherein the two sensors are used for oxygen consumption rate (OCR) measurements. For example, the difference in pO2 between the first oxygen sensor and the second oxygen sensor can be used to determine OCR of the encapsulated cells. This is a measure of tissue viability.

The sensors (e.g. oxygen sensors) may be used to help determine when the cells are dead (e.g., via oxygen sensors, etc.). Without wishing to limit the present invention to any theory or mechanism, cells are likely dead if there is generally no difference in oxygen levels inside and outside the device. Typically there is a difference (a gradient) in oxygen levels between the inside and outside of the device because oxygen is being consumed by live cells. Thus, no difference would be indicative of no oxygen consumption, thus the cells are likely dead. A bigger difference (gradient) in oxygen levels between the inside and outside of the device would indicate there are more viable cells. A user may determine how many cells are dying by determining the change in oxygen gradient.

The flow of oxygen gas into the encapsulation device can interfere with OCR measurements of the cells. Thus, the methods of the present invention comprise ceasing oxygen gas delivery to the cells. The methods for measuring OCR further comprise reducing the temperature of the encapsulation device and/or media surrounding the device to a temperature between 4 and 8 degrees C., which can help reduce metabolic rate of the cells and thus reduce their oxygen requirements (allowing the oxygen gas delivery to be shut off). The OCR measurements may be continuous. Without wishing to limit the present invention to any theory or mechanism, it is believed that keeping the temperature low during OCR measurements can help improve accuracy of the measurements since OCR measurements at higher temperatures can be affected by the depletion of oxygen within the packed cells due to the higher oxygen consumption be these cells at higher temperatures.

Measurements of potency of cells, e.g., measurements of glucose-stimulated insulin secretion (GSIS) may be made when the cells are at a temperature of about 37° C., or a temperature from 34 to 40° C. (e.g., 34° C., 35° C., C, 36° C., 37° C., 38° C., 39° C., 40° C.).

Insulin can be measured every minute or at shorter intervals or longer intervals as appropriate. Methods of measuring GSIS are known to one of ordinary skill in the art. Without wishing to limit the present invention to any theory or mechanism, it is believed that the flow of oxygen gas in the encapsulation device may be critical for proper GSIS measurements.

The present invention also features methods of helping to reduce cell damage (e.g., ischemic damage, physical damage, etc.) during loading of an encapsulation device. In some embodiments, the methods feature reducing the temperature of the cells, e.g., to a temperature from 4 to 8 degrees C. (which reduces the metabolic rate of cells). The cells may be in a media such as a conventional culture media such as serum supplemented or human serum albumin (HSA) supplemented RPMI, DMEM, or any other appropriate media. The methods may feature delivering oxygen gas to the device and or media. In some embodiments, pluronic acid is used during loading in order to avoid cell damage. This may be beneficial for optimization of cell loading. Also, it is possible that OCR measurements at low temperatures (e.g., from 4 to 8 degrees C.) may help determine the number of viable cells in a device during loading.

The disclosures of the following U.S. patents are incorporated in their entirety by reference herein: PCT/US2011/055157.

Various modifications of the invention, in addition to those described herein, will be apparent to those skilled in the art from the foregoing description. Such modifications are also intended to fall within the scope of the appended claims. Each reference cited in the present application is incorporated herein by reference in its entirety.

Although there has been shown and described the preferred embodiment of the present invention, it will be readily apparent to those skilled in the art that modifications may be made thereto which do not exceed the scope of the appended claims. Therefore, the scope of the invention is only to be limited by the following claims. Reference numbers recited in the claims are exemplary and for ease of review by the patent office only, and are not limiting in any way. In some embodiments, the figures presented in this patent application are drawn to scale, including the angles, ratios of dimensions, etc. In some embodiments, the figures are representative only and the claims are not limited by the dimensions of the figures. In some embodiments, descriptions of the inventions described herein using the phrase “comprising” includes embodiments that could be described as “consisting of”, and as such the written description requirement for claiming one or more embodiments of the present invention using the phrase “consisting of” is met.

The reference numbers recited in the below claims are solely for ease of examination of this patent application, and are exemplary, and are not intended in any way to limit the scope of the claims to the particular features having the corresponding reference numbers in the drawings. 

1. A system for measuring oxygen consumption rate (OCR) of cells, said system comprising: a. a bioreactor with an inlet and an outlet, wherein a first oxygen sensor is disposed at the inlet and a second oxygen sensor is disposed at the outlet; b. an encapsulation device comprising a lumen with the cells, and a vascularizing membrane, the encapsulation device is housed in the bioreactor; c. a heat exchanger for heating liquid media to at least one temperature from 7° C. to 27° C. and gas exchanger controlling oxygen levels from 0 to 100%; and d. a pump for pumping liquid media from the heat exchanger to the bioreactor via the inlet and out the outlet; wherein the oxygen sensors detect oxygen levels of the media for determining oxygen consumption rate of the cells.
 2. The system of claim 1 further comprising a sample removal outlet for obtaining a media sample after the outlet of the bioreactor.
 3. The system of claim 2, wherein the media sample is for measuring insulin secretion, glucagon, pancreatic polypeptide, c-peptide, a hormone, or a combination thereof.
 4. The system of claim 1, wherein the gas exchanger provides oxygen to the media from 0 to 100%.
 5. The system of claim 4, wherein oxygen production in the media can be shut off.
 6. A system for measuring oxygen consumption rate (OCR) of cells, said system comprising: a. a bioreactor with an inlet and an outlet, wherein a first oxygen sensor is disposed at the inlet and a second oxygen sensor is disposed at the outlet; b. an encapsulation device comprising a lumen with the cells, and a vascularizing membrane, the encapsulation device is housed in the bioreactor; c. a heat exchanger for heating liquid media to at least one temperature from 7° C. to 37° C. and gas exchanger controlling oxygen levels from 0 to 100%; and d. a pump for pumping liquid media from the heat exchanger to the bioreactor via the inlet and out the outlet; wherein the oxygen sensors detect oxygen levels of the media for determining oxygen consumption rate of the cells.
 7. The system of claim 6 further comprising a sample removal outlet for obtaining a media sample after the outlet of the bioreactor.
 8. The system of claim 7, wherein the media sample is for measuring insulin secretion.
 9. The system of claim 6, wherein the heat exchanger provides oxygen to the media.
 10. The system of claim 9, wherein oxygen production in the media can be shut off.
 11. A system comprising: a. a bioreactor with an inlet and an outlet, wherein a first oxygen sensor is disposed at the inlet and a second oxygen sensor is disposed at the outlet; b. an encapsulation device comprising a lumen with the cells, and a vascularizing membrane, the encapsulation device is housed in the bioreactor; c. a heat exchanger for heating liquid media to at least one temperature from 7° C. to 37° C. and gas exchanger controlling oxygen levels from 0 to 100%; and d. a pump for pumping liquid media from the heat exchanger to the bioreactor via the inlet and out the outlet; and e. a sample removal outlet for obtaining a media sample after the outlet of the bioreactor;
 12. The system of claim 11, wherein the system is for measuring oxygen consumption rate of cells, and the oxygen sensors are for detecting oxygen levels of the media.
 13. The system of claim 11, wherein the system is for measuring insulin secretion of cells.
 14. The system of claim 11, wherein the heat exchanger provides oxygen to the media.
 15. The system of claim 14, wherein oxygen production in the media can be shut off.
 16. The system of claim 1, wherein the cells are islet cells or stem cell-derived beta cells.
 17. The system of claim 1 further comprising a glucose sensor, a lactate sensor, a pH sensor, a CO₂ sensor, or a combination thereof.
 18. The system of claim 1, wherein the oxygen sensors are operatively connected to a system for regulating an amount of oxygen delivered to the cells.
 19. The system of claim 18, wherein the system for regulating an amount of oxygen delivered to the cells can adjust a level of oxygen supplied to the cells based on a command received based on an oxygen level determined by the oxygen sensors. 20.-27. (canceled) 